Planographic plate and method of making same



Patented Oet. 13, 1953 PLANOGBAPHIC PLATE AND METHOD OF MAKING SAME Douglas A. Newman, Port Washington, N. Y., alsignor to Columbia Ribbon and Carbon Manufacturing Company, Inc., Glen Cove, N. Y., a

corporation of New York No Drawing. Application December 22, 1945, Serial No. 637,087

34 Claims.

This invention relates to the manufacture of planographic printing plates, suitable for use in planographic printing processes'in which the surface of a plate on which an image is formed of ink-receptive material (usually a greasy ink) is wetted with an aqueous ink-repelling fountain fluid, then inked over to deposit ink only on the image, the latter being then transferred to a sheet of paper, usually by way of a blanket as in offset printing, the image being repeatedly reinked and the foundation being maintained wet or ink-repellent as repeated copies are printed; and to a method of pianographic printing employing printing plates prepared according to the invention.

More specifically, this invention relates to planographic printing plates having a paper foundation and a water-soluble coating thereon which can be inscribed with an oleophilic imageforming material for use in a planographic printing process of the aforesaid type, and to a process employing such plates, involving inscription of the coated plate while dry with an oleous imageforming material, insolubilizing the coating on the inscribed plate, either before, or preferably at the time of printing, by treatment with an aqueous solution of a coagulant or precipitant for said coating which may be advantageously included in the fountain fluid of the printing device, and repeatedly inking the Plate while moistened with the fountain fluid whereby ink adheres only to the inscribed image and is repelled by the moistened background, the inked image being repeatedly transferred to a copyreceiving medium.

This application is a continuation in part of my copending applications, Serial Number 581,720, filed March 8, 1945, now Patent 2,582,347 and Serial Number 586,825, filed April 5, 1945.

For successful operation, a planographic printing plate must be ink-receptive to a degree where it receives and holds the image-forming material and printing ink, and hydrophilic to a degree where it will receive and hold sufficient aqueous ink-repellent fountain solution to limit the relnking of the plate to the image. Heretofore, many proposals have been made to meet these requirements by making the plates of special materials, or impregnating or coating the plates with various films or surface strata, so that they could be inscribed or printed with ink when dry, and then wetted to render the background around the image ink-repellent. Such proposals include, for example, impregnation and coating of plates with vinyl alcohols or their polymers or derivatives, urea-aldehyde condensation products, casein and other binders, with and without flllers. These proposals have been only partially successful by reason of the fact that the plates are unstable or variable, and change their properties, especially the optimum balance of the hydrophilic and oleophilic properties required in a satisfactory planographic printing plate. Thus, plates prepared according to prior art methods change before use by aging, and also while prints are being made.

Often the surface of planographic printing plates heretofore known, when too water-absorptive, permitted the wetting solution to undermine and invade the image with the result that the image was gradually reduced or lost. When the surface was not sufliciently water-absorptive, it failed to retain sufllcient wetting solution from the fountain to repel particles of ink used to print duplicates and the ink was deposited on the background portions of the plate, producing specks which multiplied as the plates were repeatedly inked, resulting in a splotchy and objectionable background in the prints. Excessive water-absorption by the plates during use weakened the plates, so that they stretched and buckled, causing distortion of the image. Moreover, in the use of many types of plates heretofore proposed, consistently satisfactory results could not be obtained from the beginning to the end of the run, due to the fact that the coating or impregnating solution varied in concentration and character while the run was being made.

Thus, the results obtained heretofore, for reasons above stated and others, are not uniformly satisfactory or reliable, and plates apparently made or constituted in the same manner gave vastly different results, so far as fidelity of the prints to the original was concerned, and the number of prints which could be made before the quality fell below an acceptable standard.

A further deficiency in plates heretofore known lay in the fact that the special coatings provided thereon for retaining the fountain fluid so as to render the background ink-repellent, would not sustain erasure without so injuring the coated surface as to render the master copy useless, or at best usable for only a few copies. In order to make a correction, it was necessary to make a new master copy, or to repair the erased surface by applying a repair solution or coating to the erased areas, before inserting the correction. Such repaired areas had to be dried before reinscription, rendering correction of an error a timeconsuming and inconvenient operation. As a result, the user, in preparing a master, generally found it more expedient to work at much reduced speed in order to insure absence of errors and thus avoid the necessity for making corrections or retyping the master copy.

Often, the surface of planographic plates heretofore used were sensitive to soiling with finger prints or the like, which were reproduced on the printed copies. Such plates therefore required inordinate care in handling during preparation of a master copy, and up to the time they were used for printing.

I have discovered that if a printing plate, preferably having a paper foundation, is provided on its printing surface with a dry film or coating of a water-soluble carboxy-methyl cellulose compound, particularly a water-soluble salt of a carboxy-methylcellulose. an image can be inscribed, typed or printed thereon, with an oleous image-forming material. (By carboxy-methyl cellulose, I mean a carboxy-methyl ether of cellulose.) The carboxy-methyl cellulose compound contained in the coating is then insolubilized, for example by treatment with an aqueone solution of a precipitant or coagulant for carboxy-methyl cellulose, which can be advantageously included in the aqueous fountain solution of the printing machine, and the plate used for duplication of the image, in the manner above described. The soluble carboxy-methyl cellulose coating remains stable and does not change during storage. Moreover, after insolubilization the properties of the coating remain unchanged, e. g. while the plate is being used. The absorption of water from the fountain solution employed in printing is retarded and reduced by the coatings provided in accordance with my invention, so that troubles heretofore experienced involving reduction or loss of the image do not occur. At the same time, the background portion of the plate consistently maintains its hydrophilic ink-repellent character, preventing background specks from forming, and consistently retains a true image applied to it on the surface of the coating.

I have found that planographic printing plates having especially desirable properties can be prepared by coating a paper foundation with a composition comprising a solution of a water-soluble salt of a carboxy-methyl cellulose, for example, a sodium salt or an alkaline (e. g. ammoniacal) solution of an aluminum salt, and drying the plate to form a film or coating containing the water-soluble carboxy-methyl cellulose compound. Such plates are adapted to receive an image inscribed or imprinted thereon with an oleophilic or oleous image-forming medium. and to retain the image tenaciously, after the coating is insolubilized during printing. The uninscribed background when moistened with the aqueous fountain solution consistently repels the printing ink yielding clear backgrounds, even when used for printing an exceedingly large number of copies. Such plates are not subject to aging, and do not change their characteristics when stored for an indefinitely long period.

Plates prepared in accordance with my invention are very clean to handle so that they do not show thumb prints or finger marks, which usually appear on metal plates or other coated lithographic plates. In addition, errors may be easily deleted with a pencil eraser, several times at the same place on the sheet if necessary, without injuring the ink-repellent or image-receptive properties of the background, and without causing any perceptible change in the resulting copies after the correction is made. This is especially advantageous, in that a typist can prepare master copies at normal speed, since minor errors can be readily corrected and do not neces- 4 sitate retyping or reprinting the entire copy. or a tedious repair operation after erasure.

Planographic plates can be prepared in accordance with my invention in a number of ways. The simplest, and therefore the preferred, method involves coating the paper with an aqueous composition containing a water soluble carboxy-methyl cellulose salt or compound dissolved therein, and drying the resulting coating. The coating composition is applied to the paper preferably in the form of a continuous web from which the plates can be later cut, for example, by brush-coating or tub-sizing methods. It is desirable to apply the coating of water-soluble carboxy-methyl cellulose compound in more than one layer, in order to insure sealing pin-holes which may occur in the surface if the coating is applied in a single operation. Thus paper which has been brush-coated with the carboxy-methyl cellulose solution and dried is preferably given a second coating with a similar composition, and again dried to insure formation of .a continuous film or coating. Advantageously. the paper may be calendered after each coating operation.

Before coating or after the intermediate or final drying, or after calendaring, the sheet may be provided with a water-resistant backing, for example, by coating with a solution of a waterrepellent, resinous or plastic material in a volatile organic solvent, e. g. a solution of Styron (i. e. a resinous styrene polymer) in ethyl acetate. A Styron backing has been found especially satisfactory in that it not only Waterproofs the back of the plate but gives it additional body without too much stiffness which would interfere with convenient handling of the plate in a typewriter or printing machine.

The coating composition employed in accordance with my invention preferably contains, in addition to a water-soluble carboxy-methyl cellulose compound, an inert filler such as colloidal clay, barium sulphate, calcium carbonate or the like to provide a surface having a substantial tooth, which possesses improved holding power for the ink applied to the image. Moreover, plasticizers such as giycerine can be included in the composition to insure or maintain the pliability of the film. Readily volatile alcohols such as methanol or ethanol can also be included in the mixture to accelerate drying of the film or coating.

In making a planographic plate for commercial use. it is desirable that the foundation sheet be made of paper having relatively low water absorption and relatively high wet strength, so that the plate will have suilicient body to be conveniently handled and applied to the printing press, and will have sufficient resistance to mechanical abrasion in use. To provide such a foundation sheet or continuou strip from which the sheet may be cut, a water leaf strip from a paper-making machine may be passed through a size tub containing a solution for increasing the wet strength of the paper. Preferably, how ever, a fiber-bonding absorption-limiting material is included in the pulp and the paper is formed as a wet-strength limited-absorption paper. Thus, as set forth in my copending application, Serial Number 586,825, a material such as a melamine or urea-formaldehyde resin, or a reaction product of these materials with a carboxy-methyl cellulose compound can be incorporated in the paper as a fiber-bonding waterabsorption-limiting material, either by addition to the pulp before the paper is prepared, or by impregnation after the pa 8 formed- W the web thus prepared is heated and dried, the aforesaid materials become coagulated or hardened and the paper foundation has its fibers bonded together and rendered resistant to penetration by water.

The following examples, wherein parts and percentages are by weight, will serve to illustrate planographic printing plates made in accordance with my invention.

Example 1 Calendered water leaf sheets. prepared from long-fibered pulp to which a melamine resin is added during manufacture to improve the wet strength of the resulting paper, is brush-coated with a composition made by dissolving the aluminum salt of carboxy-methyl cellulose in aqueous ammonia, adding a plasticizer and a lower alcohol, and mixing colloidal clay with the resulting solution until a uniform slurry is obtained. The mixture has the following composition:

180 parts of the aluminum salt of carbon-methyl cellulose 463 parts of methyl alcohol 90 parts of aqueous ammonia (containing about 28%% of NH3) 5238 parts of water 180 parts of colloidal clay After coating the paper with the foregoing composition, it is dried and calendered. The paper s again brush-coated with the same composition, redried, and again calendered. After drying and caiendering the back of the sheet is advantaeously coated with a 20% solution of Styron in ethyl acetate.

Example 2 Paper suitable for the foundation of a pianographic printing plate, e. g. paper of the type employed in Example 1, is brush-coated with a uniform slurry composed of z 100 parts of a aqueous solution of low viscosity sodium carboxy-methyl cellulose 20 parts of China clay 3 parts of glycerine After drying and calendtting the sheet, it is again brush coated with the same composition and again dried and calendered. The sheet thus prepared is likewise advantageously provided as in Example 1 with a water-resistant backing of Styron.

Example 3 A high wet strength low water-absorptive paper is brush coated with a 3 to 5% solution of low viscosity sodium carboxy-methyl cellulose, and the coated paper dried and calendered. The foregoing operations are repeated to insure formation of a continuous film of sodium carboxymethyl cellulose. The rear surface of the paper can then be given a coating of Styron or other waterproofing composition as disclosed in the foregoing examples.

Instead of employing a solution of sodium carboxy-methyl cellulose, a l to 3% solution of aluminum carboxy-methyl cellulose in dilute aqueous ammonia or borax solution can be used in the foregoing example. In general the concentration of water-soluble carboxy-methyl cellulose compound in the aqueous solution employed to form the coating composition is preferably about 3 to 5% in the case of the sodium compound or about 6 l to 3% in the case of the aluminum compound (which is dissolved in an aqueous alkaline solution such as ammonia).

The coating on the paper preferably amounts to about eight to nine pounds or more, per ream of 24" x 38" sheets. The amount of coating can be readily controlled by adjusting the proportions of ingredients in the coating composition, varying the number of coatings, or the amount of composition applied in each coating treatment. In the foregoing examples, each brush-coating treatment results in formation of a coating of about four pounds per ream, sb that the two treatments described produce a coating on the finished sheets of about eight pounds per ream.

When a plate prepared in accordance with my invention, such as those prepared as described in the foregoing examples, is to be used for printing, the coated printin surace thereof is typed, imprinted or inscribed with the desired image, usin an oleophiiic or oleous ink-retaining, waterrepellent, image-forming medium, e. g. a greasy ink. In the preferred method of printing, the inscribed plate or master copy, is fastened on the cylinder of a planographic printing machine, and moistened with an aqueous fountain fluid containing a. coagulant or precipitant for the carboxy-methyl cellulose. Then a fountain solution prepared by diluting a 6% aqueous solution of aluminum sulphate with about 10 to 15 times its volume of water can be used. Other precipitant salts or metal compounds can be used in the fountain solution, for example ferric chloride, copper sulphate, chromic acid, or the like, advantageously in concentration of the same order as that employed in the case of aluminum sulphate. Moreover, mineral acids such as hydrochloric or sulphuric acid, and certain organic acids such as tartaric, citric or tannic acids can be used instead of, or in conjunction with precipitant metal salts. Care must be taken, however, to avoid use of acid solutions or metal salts which would corrode or plate out on the metal part of the machine which come in contact with the fountain solution. Aluminum sulphate is especially adapted for use in view of its lack of any substantial tendency to attack metals normallv used in constructing the printing equipment. If desired, the fountain solution can also contain inert ingredients, sometimes employed in solutions for planographic printing, such as watersouble gum thickeners, wetting agents or the li e.

The insolubilizing component of the fountain solution coagulates or insolubilizes the watersoluble carboxy-methyl cellulose compound of the coating, and after the initial reaction, the composition of the fountain solution remains unchanged, so that upon continued use of the plate for printing. durin which it is repeatedly moistened with fountain solution, no alteration takes place in the solution which would cause variations in the master copy, or the duplicate copies obtained therefrom.

In the course of the printin oleous ink is applied from an inking roller to the image-bearin surface of the plate, the ink adhering only to those portions of the plate which are inscribed ith the oleous ima e, while being repelled b the background portions of the plate, constituted by the coating moistened with the aqueous fountain solution. The inked image is then transferred to copy-receiving medium such as a printing blanket, used in offset printing, and then applied to the sheet on which the copy of the image is to be made. Planographic plates p pared in accordance with this invention can be employed for making 6000 to 10,000 copies without substantial deterioration in the quality of the duplicate copies of the image. If desired, the inked plate can also be applied for direct printing of copies, the image in this case being the reverse of the matter to be duplicated on the copies.

Alternatively, the coated plate bearing the oleous image can be subjected to an insolubilizing treatment prior to its use for. printing. For example the plate can be moistened or washed with an aqueous solution containing a coagulant or precipitant salt or acid as disclosed above for use in the fountain solution; or more concentrated solutions (e. g. having a concentration of about of precipitant metal salts such as aluminum sulphate, copper sulphate, ferric chloride. or chromium trioxide or mixtures of such salts as employed in my copending application, Serial Number 637,088, can be applied to the coated image-bearing surface of the plate. The plate can then be employed in a planographic printing machine, with or without drying, and moistened with water alone or water containing the usual fountain fluid ingredients. If the plate is dried, after the insolubilizing treatment, additional image-forming matter can be inscribed thereon for reproduction.

Variations and modifications can be made in the foregoing examples and procedure without departing from the scope of the invention, as will be obvious to those skilled in the art. Thus, other soluble salts of carboxy-methyl cellulose, such as the ammonium, calcium or magnesium salt, can be used instead of the sodium or am monium-aluminum salt in preparing the coating composition for the paper. The penetrationresistant backing of water-proofing plastic (e. g. Styron) can be applied either before or after the carboxy-methyl cellulose coating is formed on the printing surfaceof the paper.

High wet-strength paper for use as a foundation for the plates of my invention can be advantageously made as disclosed in my copending application, Serial Number 586,825, by combining a concentrated melamine preparation (e. g. the product commercially available under the name of Melmac No. 7270) with a. 2% aqueous solution of the sodium salt of a carboxy-methyl cellulose; grinding the resulting precipitate to a colloidal slurry, adding the slurry to the paper pulp so as to incorporate it in the paper, or impregnating the paper as it leaves the paper machine by applying the slurry thereto in a size tub. and drying and heating the paper to cause bonding of the fibres by the added material, thus forming paper of high wet-strength and resistance to water absorption. Instead of using a precipitate of melamine-carboxy-methyl cellulose, a solution formed by mixing Melmac No. 7277 with a 2% solution of sodium carboxy-methyl cellulose can be added to the paper pulp or used to impregnate the paper from a size tub. Methylol-urea or lower urea-formaldehyde polymers can be used instead of melamine resins.

If desired, the paper foundation can be printed or inscribed with an oleous image-forming medium to produce a water-repellent image before application or the water-soluble carboxy-methyl cellulose solution or composition, the latter being repelled by the image and thus coating only the uninscribed portion of the plate. After drying and calendering, the uninscribed portions of the plate can then be inscribed with an image-form- 8 ing medium in accordance with this invention. and the plate can be used to make cop 0! the pro-formed as well as the later-formed images in the manner described above.

I claim:

1. In a planographic printing plate having a foundation, a dry, oleophilic image-receptive, hydrophilic background-forming coating on said foundation, comprising a water-soluble carboxymethyl cellulose compound; and an ink-receptive water-repellent image on said coating.

2. In a planographic printing plate, an oleophilic image-receptive, hydrophilic backgroundforming coating, comprising a water-soluble salt of a carboxy-methyl cellulose; and an ink-receptive water-repellent image on said coating.

3. In a planographic printing plate having a foundation, a dry, oleophilic image-receptive hydrophilic background-forming coating on said foundation, comprising a water-soluble material including a salt of a carboxy-methyl cellulose with aluminum in combination with a cation of the group consisting of alkali metals and ammonium; and an ink-receptive water-repellent image on said coating.

4. A planographic printing plate comprising a foundation of paper having high-wet strength and resistant to water absorption; a dry coating thereon constituting an oleophilic image-receptive, hydrophilic background-forming printing surface, comprising a water-soluble carboxymethyl cellulose compound; and an ink-receptive water-repellent image on said coating.

5. A planographic master which comprises a paper foundation and a dry coating thereon constituting an oleophilic image-receptive, hydrophilic background-forming printing surface, comprising a water-soluble carboxy-methyl cellulose compound, and a water-repellent ink-receptive image inscribed on the surface of said coating.

6. A planographic master which comprises a paper foundation, 9. dry coating thereon constituting an oleophilic image-receptive, hydrophilic background-forming printing surface comprising a water-soluble salt of a carboxy-methyl cellulose. and a water-repellent ink-receptive image inscribed on the surface of said coating.

7. The method of making a planographic printing plate which comprises coating the surface of a foundation of paper having high-wet strength and resistance to absorption, and having a moisture-proof coating on the rear surface thereof as a backing, with a composition comprising an aqueous solution of a water-soluble carboxy-methyl cellulose compound. drying said composition on the surface of said foundation; and forming an ink-receptive, water repellent image on the surface of the water-soluble coating.

8. The method of making a planographic printing plate which comprises coating the surface of a paper foundation with successive layers of a composition comprising an aqueous solution of a water-soluble carboxy-methyl cellulose compound, drying said composition on the surface of said foundation after application of each layer: and forming an ink-receptive, water repellent 11:18.88 on the surface of the water-soluble coat- 9. The method of making a planographic printing plate which comprises coating the surface of a paper foundation with a composition comprising an aqueous solution of a water-soluble carboxy-methyl cellulose compound, and drying said com osition on the surface of said foundation,

the amount of said composition being such as to yield a coating of about 4 pounds per ream of 24" x 38" sheets; repeating the foregoing coating and drying operations so as to form a coating of about 8 to 9 pounds per ream of 24" x 38" sheets; and forming an ink-receptive, water repellent image on the surface of the water-soluble coating.

10. The method of making a planographic printing plate which comprises coating the surface of a paper foundation with a composition comprising an aqueous solution of a water-soluble salt of a carboxy-methyl cellulose, glycerine as a plasticizer and colloidal clay as a filler suspended therein, drying said composition on the surface of said foundation, the amount of said composition being such as to yield a coating of about 8 to 9 pounds per ream of 24" x 38" sheets; and forming an ink-receptive, water repellent image on the surface of the water-soluble coating.

11. In the art of planographic printing, a process which comprises providing on the surface of a planographic printing plate a dry coating containing a water-soluble carboxy-methyl cellulose compound, forming an oleophilic image on the surface of said coating, and treating said surface with an aqueous solution containing a coagulant for the carboxy-methyl cellulose compound.

12. In the art of planographic printing, a process for preparing a master which comprises providing on the surface of a paper foundation a dry coating containing a water-soluble salt of a carboxy-methyl cellulose, forming a water-repellent ink-receptive image on the surface of said coating, and treating the coated surface of the foundation with an aqueous solution containing a coagulant for said carboxy-methyl cellulose salt.

13. In the art of planographic printing, a process for preparing a master which comprises providing on the surface of a planographic printing plate a dry coating containing a water-soluble carboxy-methyl cellulose compound, forming a water-repellent ink-receptive image on the surface of said coating, and treating the surface of said plate with an aqueous solution containing a coagulant metal salt for said carboxy-methyl cellulose compound.

14. In the art of planographic printing, a process for preparing a master which comprises providing on the surface of a planographic printing plate a dry coating containing a water-soluble carboxy-methyl cellulose compound, forming a water-repellent ink-receptive image on the surface of said coating, and treating the surface of said plate with an aqueous solution containing a coagulant acid for said carboxy-methyl cellulose compound.

15. In the art of planographic printing, a process for preparing a master which comprises providing on the surface of a planographic printing plate a dry coating containing a water-soluble carboxy-methyl cellulose compound, forming a water-repellent ink-receptive image on the surface of said coating, and treating the surface of said plate with an aqueous solution containing aluminum sulphate.

16. The method of printing duplicates by the planographic method which includes forming an ink-receptive, water-repellent image on a pianographic printing plate having on the printing surface thereof a dry coating containing a watersoluble carboxy-methyl cellulose compound, moistening said surface with an aqueous solution containing a coagulant for said carbon-methyl 10 cellulose-compound, applying oleous printing ink to the moistened image-bearing surface of the plate to ink the image, transferring the ink from the image to a copy-receiving medium, and maintaining the surface of said plate wet and reinking the image as additional duplicates are made.

17. The method of printing duplicates by the planographic method which includes forming an ink-receptive, water-repellent image on a pianographic printing plate having on the printing surface thereof a dry coating containing a watersoluble salt of a carboxy-methyl cellulose, moistening said surface with an aqueous solution containing a coagulant metal salt for said carboxymethyl cellulose salt, applying oleous printing ink to the moistened image-bearing surface of the plate to ink the image, transferring the ink from the image to a copy-receiving medium, and maintaining the surface of saidplate wet and reinking the image as additional duplicates are made.

18. The method of printing duplicates by the planographic method which includes forming an ink-receptive, water-repellant image on a pianographic printing plate having on the printing surface thereof a dry coating of a water-soluble salt of a carboxy-methyl cellulose, treating said surface with an aqueous solution containing aluminum sulphate, applying oleous printing ink to the image-bearing surface of the plate to ink the image, transferring the ink from the image to a copy-receiving medium, and maintaining the surface of said plate wet and re-inking the image as additional duplicates are made.

19. A planographic printing plate comprising a paper foundation having incorporated with the fibers thereof a binder of the group consisting of melamine resins, urea-formaldehyde resins and compounds of said resins with a carboxymethyl cellulose compound; a dry coating on the front surface of said foundation, constituting an oleophilic image-receptive, hydrophilic backgroundforming printing surface, comprising a water-soluble carboxymethyl cellulose compound; and an ink-receptive water-repellent image on said coating.

20. The method of making planog' aphic printing plates having an oleophilic image-receptive, hydrophilic background-forming printing surface thereon, which comprises applying to a plate an aqueous solution of a water-soluble carboxymethyl cellulose which dries as a water-soluble coating, drying said coating to render the coating receptive to image-forming material, and forming an ink-receptive water-repellent image on the surface of the dry water-soluble coating.

21. The method of making planographic printing plates having an oleophilic image-receptive, hydrophilic background-forming printing surface thereon, which comprises applying to a plate an aqueous solution of a water-soluble carboxymethyl cellulose which dries as a watersoluble coating, drying said coating to render the coating receptive to image-forming material, forming an ink-receptive water-repellent image on the surface of the dry water-soluble coating. and treating said coating with an aqueous solution containing a coagulant for said carboxymethyl cellulose compound to render said coating water-insoluble.

22. The method of making planographic printing plates having an oleophilic image-receptive, hydrophilic background-forming printing surface thereon, which comprises applying to a plate an aqueous solution of a water-soluble carboxymethyl cellulose which dries as a watersoluble coating, and drying said coating to render the coating receptive to image-forming material, forming an ink-receptive water-repellent image on the surface of the dry water-soluble coating, dampening the printing surface of the plate with an aqueous solution containing a coagulant for said carboxymethyl compound to render the background-forming portions of said coating water-insoluble and repellent to oleous ink, and while the plate is so dampened applying oleous ink to the printing surface to be deposited on the image.

23. The method of making planographic printing plates having a water-soluble oieophiiic image-receptive, hydrophilic background-forming printing surface thereon, which comprises applying to the plate an aqueous solution of an aluminum salt of carboxymethyl cellulose in combination with a cation of the group consisting of alkali metals and ammonium which dries at normal temperature as a water-soluble coating; drying said coating to render. the coating receptive to image-forming material; and forming an ink-receptive water-repellent image on the surface of the coating.

24. The method of making planographic printing plates having a water-soluble oieophiiic image-receptive, hydrophilic background-forming printing surface thereon, which comprises applying to the plate an aqueous solution of a sodium salt of carboxymethyl cellulose which dries as a water-soluble coating; drying said coating to render the coating receptive to imageforming material; and forming an ink-receptive water-repellent image on the surface of the coating.

25. The method of making planographic printing plates having a water-soluble oieophiiic image-receptive, hydrophilic background-forming printing surface thereon, which comprises applying to the plate an aqueous solution of a water-soluble salt of carboxymethyl cellulose, which solution dries as a water-soluble coating; drying said coating to render the coating receptive to image-forming material; and forming an ink-receptive water-repellent image on the surface of the coating.

26. The method of making a planographic printing plate presenting water receptive areas which includes the steps of coating a surface of the plate with a film of a water soluble carboxymethyl cellulose product, applying an ink-receptive water-repellent image to said film. and thereafter rendering said film water insoluble.

27. The method of making a planographic printing plate presenting water receptive areas which includes the steps of coating a surface of the plate with a film of a water soluble carboxymethyl cellulose product, applying an ink-receptive water-repellent image to said film, and thereafter treating the film with a reagent to render the same water insoluble.

28. The method of making a planographic printing plate presenting water receptive areas which includes the steps of coating a surface of the plate with a film of a water soluble carbonymethyl product, applying an ink-receptive waterrepellent image to said film, and thereafter treating said film with an acid solution to coagulate the carboxymethyl cellulose product and render said film water insoluble.

29. The method of making a planographic printing plate presenting water receptive areas 12 which includes the.steps of coating a surface of the plate with a film of a water soluble carboxymethyl cellulose product, applying an ink-receptive water-repellent image to said film, and rendering said film water insoluble by including an insolubilizing agent in the fountain fiuid of the printing machine with which the plate is used.

30. As a new article of manufacture and sale. a planographic printing plate comprising a. foundation, and a dry film on the surface of aid foundation containing an insolubilizable carbonymethyl cellulose compound as the essential filmforming component thereof, said film being greaseand water-receptive when dry and grease repellent when wet; and an ink-receptive waterrepellent image on said film.

31. As a new article of manufacture and sale, a planographic printing plate comprising a foundation, and a dry film on the surface of said foundation containing sodium carboxymethyl cellulose as the essential film-forming component thereof, said film being greaseand water-receptive when dry and grease repellent when wet; and an ink-receptive water-repellent image on said film.

32. As a new article of manufacture and sale, a planographic printing plate comprising a foundation, and a dry film on the surface of said foundation containing ammonium carboxymethyl cellulose as the essential film-forming component thereof, said film being greaseand waterreceptive when dry and grease repellent when wet; and an ink-receptive water-repellent image on said film.

33. The method of making a planographic printing plate which comprises coating a foundation with an aqueous film-forming solution containing a salt of a carboxymethyl cellulose as the essential film-forming component thereof, drying said coating to form a film; applying an ink-receptive, water-repellent image to the surface of said film; and thereafter rendering said film water-insoluble.

34. In the process of planographic printing, the steps which comprise forming a plate hav ing a foundation and a film on a surface of said foundation comprising a water-soluble carboxymethyl cellulose compound as the essential filmforming component thereof. said film being grease-receptive and water-receptive when dry and grease repellent when wet and forming the printing surface of said plate; applying an inkreceptive water-repellent image to the surface of said film wetting said plate with an aqueous fountain solution containing a reagent for rendering said carboxymethyl cellulose compound water-insoluble; and applying a printing ink to said image for transfer to a copy sheet.

DOUGLAS A. NEWMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,154,219 Shepherd Apr. 11, 1939 2,236,545 Maxwell Apr. l, 1941 2,311,889 Toland Feb. 23, 1943 2,370,517 Bass et al Feb. 27, 1945 2,542,784 Van Dusen Feb. 20, 1951 OTHER REFERENCES Sodium Carboxymethylcellulose Hercules Powder 00., Wilmington, Delaware. Copy in Div. 64.

Ser. No. 397,138, Finkentacher (A. P. 0.), published May 11, 1943.

Certificate of Correction Patent No. 2,655,101 October 13, 1953 Douglas A. Newman It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 8, line 12, for late, an read plate having a foundation, a dry,; line 14, after coating and efore the comma insert on said foundation; line 28, for resistant read resistance;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 22nd day of December, A. D. 1953.

ARTHUR W. CROCKER,

Assistant Commissioner of Patents. 

1. IN A PLANOGRAPHIC PRINTING PLATE HAVING A FOUNDATION, A DRY, OLEOPHILIC IMAGE-RECEPTIVE, HYDROPHILIC BACKGROUND-FORMING COATING ON SAID FOUNDATION, COMPRISING A WATER-SOLUBLE CARBOXYMETHYL CELLULOSE COMPOUND; AND AN INK-RECEPTIVE WATER-REPELLENT IMAGE ON SAID COATING.
 26. THE METHOD OF MAKING A PLANOGRAPHIC PRINTING PLATE PRESENTING WATER RECEPTIVE AREAS WHICH INCLUDES THE STEPS OF COATING A SURFACE OF THE PLATE WITH A FILM OF WATER SOLUBLE CARBOXYMETHYL CELLULOSE PRODUCT, APPLYING AN INK-RECEPTIVE WATER-REPELLENT IMAGE TO SAID FILM, AND THEREAFTER RENDERING SAID FILM WATER INSOLUBLE 